Patent GB-864490-A (GB)
Title: Improvements relating to shaft positioning mechanism for machine tool control apparatus
Inventor: FOSSEY FREDERICK AMBROSE
IPC: B23Q5/00
Filed: 1958-06-20
Abstract: 864,490. Gearing for stopping and starting machinery; shaft couplings; friction clutches. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. June 20, 1958, No. 19862/58. Class 80 (2). A shaft 4 for adjusting an automatic machine tool coordinate setting system under the control of punched card apparatus comprises a driving sprocket 8 connected to rotate with the shaft by energization of a solenoid 13 engaging an electromagnetic clutch 12 having a driven member consisting of a peripherally notched disc 11, secured to the shaft and adapted to be engaged by a detent 22 which can be held against the bias of a spring 23 in its disengaged position by energizing an electromagnet 25, a projection 19 fast upon the notched disc 11 coacting with a stop (not shown) carried by an end-plate 2 supporting the apparatus to limit the turning motion of the shaft to less than 360 degrees. The driving sprocket 8 is engaged by a chain passing over a guide 9 and secured to a reciprocating table carrying the punched cards. The movement of the sprocket 8 is limited to approximately 360 degrees by the length of travel of the punched card table. On initiation of rotation of the shaft 4 to a new setting, the reciprocating punched card table moves backwards from its operative position and turns the clutch driving member 12, a projection 20 thereon engaging the projection 19 upon the peripherally notched disc 11 to restore the latter to a zero position. Rotation of the disc 11 pivots the detent arm 22 to the disengaged position, and the electromagnet 25 is energized so that the detent is held clear of the disc notches. At the end of the return stroke, the punch card table is driven forwards whereby the chain drives the sprocket 8 and, through the now engaged electromagnetic clutch 12, turns the disc 11 and the shaft 4. When a hole in a card carried by the table arrives at a datum position and is there sensed by a reader, the clutch solenoid 13 and the detent electromagnet 25 are simultaneously deenergized, as by the actuation of a relay, so that the detent 22 engages a notch on the disc 11 to hold the shaft 4 at the required angular position. Current is fed to the clutch solenoid 13 through two oppositely wound phosphor-bronze strips 14 located in insulated channels 15 and connected to a terminal block 16. The detent 22 comprises a roller 24 which engages the notches on the disc 11, friction thereby being reduced. The shaft 4 carries an indicating disc 27 bearing numbers corresponding to the angular positions in which the shaft is to be located. Within the shaft 4, which is hollow, is a spindle 5 carrying at one end a small knob 6 and at the other an arm 30, having at one side a bracket 34 toothed at 35 to engage peripheral teeth on a disc 28 secured to the shaft 4, and at the other side a bracket 32 carrying a pin 33 for engagement in holes 29 spaced around the disc 28 at angular positions corresponding to the angular positions in which the shaft 4 is to be retained. A spring 31 biases the spindle 5 axially within the shaft 4 to retain the pin 33 in the selected hole 29 and the teeth 35 in engagement with the teeth around the disc 28. By pulling the knob 6 against the bias of the spring 31, the teeth 35 and the pin 33 can be disengaged from the disc 28, so that the knob 6 and the spindle 5 can be turned to such a position that the pin 33 then engages another of the holes 29. The angular position of the spindle 5 and the arm 30 is thereby adjusted relatively to the hollow shaft 4, so that a selsyn rotor driven from the arm 30 is correspondingly adjusted. A number of similar shaft positioning mechanisms may be provided, each driven by the chain engaging the sprocket 8 and connected to the reciprocating punched card table. Specification 764,588 is referred to.